Ratio scale



D. K. CROOK RATIO SCALE June 26, 1951 Filed Aug. 10, 1948 2 Sheets-Sheet 1 WK mm 3 R N K a XMMW ATTORNEYS June 26, 1951 D. K. CROOK RATIO SCALE 2 Sheets-Sheet 2 Filed Aug. 10, 1948 3mm D,K.CROOK ATTORNEYS Patented June 26, 1951 UNITED STATES PATENT OFFICE RATIO SCALE David K. Crook, Lincoln, Nebr.

Application August 10, 1948, Serial No. 43,502

4 Claims. (01. 33-75) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, if patented in any country may be manufactured and used by or for the Government of the United States of America for governmental purposes throughout the world Without the payment to me of any royalty thereon.

This invention relates to a device for use as a proportional divider, or in drafting enlargements or reductions of drawings, maps, or templates, to scale.

An object of this invention is a scaling device of this character having simplicity of design and ruggedness of construction, combined with accuracy and adjustability to vary the scale ratio.

Two modifications of the device are shown in the drawings, in which:

Figure 1 is a top three-dimensional view of one form;

Figure 2 is a section on line 2-2 of Figure 1;

Figure 3 is a detail View of gears of Figure 1;

Figure 4 is a top view of the second form;

Figure 5 is a section on line 55 of Figure 4;

Figure 6 is a section on line 56 of Figure 4;

Figure 7 is a detail view of a gear of Figure 4 and its mounting.

The device shown in Figure 1 comprises a base plate I having a bevelled straight-edged surface 2 which may be ruled if desired. Attached to plate I is a pointer 3 having a hole 4 through which a pin point may be projected. The instrument may be pivoted about this point on the map or drawing to be reduced or enlarged.

Base plate I is provided with two parallel slots, or grooves, 5 and 6. In slot 5 is slidably seated a gear-toothed rack I which meshes with a lower pinion gear 8. A second gear-toothed rack 9 is slidably seated in slot 6, and meshes with an upper gear I 0. As shown in Figure 2, slot 5 is deeper than slot 6, to permit access of the gear 8 to rack "I.

Gear It is rotatably mounted upon shaft I I, which is fixed upon base plate extension I2. Gear 8 is mounted upon shaft I 3 attached to base plate extension I2. Gears I 4 and I5 rotate about shaft I6, which is mounted upon lever II. A pin I5 on gear I5 fits into a hole in gear I4. Lever II pivots on shaft I3 at one end; at its other end is a screw I8 which may be fastened in place in any one of the three holes I9, 20, 2|. Gear I5 may be replaced with a smaller or a larger gear having a different number of teeth. The gear ratio may thus be adjusted to obtain the desired enlargement or reduction.

Pointer 22 is attached to and moves with rack bar I. Pointer 23 is attached to rack bar 9.

To operate the device of Figure 1 it is placed Over the center point of the map, or drawing, or over the picture center of a templet. A pin is then inserted through hole 4. Pointer 22 is moved along edge 3' to a selected point on the map. Pointer 23 will follow along edge 3' a proportional distance, dependent upon the over-all gear ratio.

The device shown in Figure 4 is similar in structure and operation. The mounting of the gears is modified. The gear 3I rotates about a shaft 25 which is fixed upon slide plate 26. The plate 26 slides upon the base plate I, being held in position by screws 21 tightened in slot 28. By replacing gear 32 by a smaller or larger gear the ratio between the distances moved by pointers 22 and 23 can be altered. Lower pinion gear 29 meshes with lower rack I and with large gear 30. Gear 3| meshes with upper rack 9 and with gear 32. Gear 32 is fixed upon larger gear 33 by pin 33 fitting in a hole in gear 33.

Having thus described my invention, I claim:

1. In a proportional divider, a base member providing a ruling straight edge and two grooves parallel thereto, a straight rack slidably mounted in each groove, a pinion gear in mesh with each rack, both pinions being mounted upon the base member at the same side of the straight-edge, the gear teeth of the rack nearer the straight edge extending vertically below the path of the teeth of the other rack to permit access of one of the said pinions thereto, additional gears to transmit movement of one of the pinions to the other in the same direction, and a pointer mounted upon each rack and travelling along the straight edge, the pointer attached to the farther removed rack moving in a path adjacent to but outside the path of the other pointer, which latter is nearer the straight edge, the additional gears comprising a pair of rotary gears mounted for rotation together about a common pivot, a lever pivoted upon the shaft of one of the pinion gears, the said common pivot being carried by the lever.

2. In a proportional divider, a base member providing a ruling straight edge and two grooves parallel thereto, a straight rack slidably mounted in each groove, a pinion gear in mesh with each rack, both pinions being mounted upon the base member at the same side of the straight-edge, the gear teeth of the rack nearer the straight edge extending vertically below the path of the teeth of the other rack to permit access of one of the said pinions thereto, additional gears to transmit movement of one of the pinions to the other in the same direction, and a pointer mounted upon each rack and travelling along the straight edge, the pointer attached to the farther removed rack moving in a path adjacent to but outside the path of the other pointer, which latter is nearer the straight edge, the additional gears comprising a pair of rotary gears mounted for rotation together about a common pivot, one of said four gears being mounted upon an axis adjustable in position with respect to the axis of another of said four gears with which it is in mesh in operation, whereby one of said gears may be replaced by another gear, for adjustment of over-all gear ratio.

3. The device of claim 2, one of the pinion gears being the gear mounted upon an axis adjustable as recited, said one pinion gear being mounted upon a shaft adjustable longitudinally of the racks.

4. A ratio scale comprising a base plate providing a longitudinally extending ruling straight edge having a fined pivot point marker intermediate its ends; and providing two grooves parallel to and both on the same side of the straight edge; a first straight rack gear slidably mounted in the groove that is nearer the straight edge; a second straight rack gear slidably mounted in the other groove; the teeth of the gear of the first rack extending below the plane of the lower face of the second rack gear; a pinion gear mounted on the base plate in mesh with the second rack gear, another pinion gear mounted on the base plate beneath the second rack gear and in mesh with the first rack gear; a pair of gears, mounted for rotation about a common axis for transmitting proportionate motion of one rack gear to the other, these gears meshing with the pinion gears and moving the racks in the same direction on the same side of the fixed pivot point marker; a first pointer attached to the first rack and travelling along the straight edge; a second pointer attached to the second rack and mounted to travel along the straight edge above the path of the first pointer.

D. K. CROOK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 229,777 Villa July 6, 1880 871,333 Giambra Nov. 19, 1907 1,062,700 Firsching May 27, 1913 1,19Q,61G Reilly et a1 Sept. 26, 1916 1,341,865 Solberg June 1, 1920 1,703,736 Jacob Feb. 26, 1929 1,797,551 Heinze Mar. 24, 1931 2,291,552 Lalonde July 28, 1942 FOREIGN PATENTS Number Country Date 11,267 Great Britain May 11, 1912 

